Method for fastening an engaging member to a cylinder

ABSTRACT

A method for forming a cylindrical structure by fastening an engaging member to an open end of a cylinder, including the steps of preparing an inner surface at the open end of the cylinder to provide the cylinder with a reduced thickness, providing an engaging member having a plurality of discrete recesses formed circumferentially around the periphery of the engaging member, and fitting the engaging member into the processed open end of the cylinder. The invention further comprises bending and cutting the processed open end of the cylinder around the open end of the cylinder such that plural projections project into the recesses of the engaging member. In this manner the engaging member is restricted from relative movement between the cylinder and the engaging member in both the longitudinal and rotational directions.

This application is a continuation application of application Ser. No.08/125,858, filed Sep. 24, 1993, now abandoned.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to a method of fastening an engagingmember to an end of a cylinder, a cylindrical structure thus formed, aprocess cartridge and an image forming apparatus including thecylindrical structure.

Herein, the image forming apparatus may for example include a laser beamprinter, an electrophotographic copying machine, a facsimile apparatusand a word processor. The cylindrical structure may for example includea photosensitive drum, a conveying roller, a fixing roller and adeveloping sleeve for such image forming apparatus.

Hereinbelow, the description will be made principally based onproduction of a photosensitive drum as an example of the cylindricalstructure. It is however to be understood the present invention is notrestricted thereto but can be widely applicable to production ofapparatus for forming images on recording media and parts thereof.

Hitherto, a cylindrical electrophotographic photosensitive member(hereinafter sometimes called a "photosensitive drum") has been formedby providing both ends of a cylinder having a peripheral surface coatedwith a photoconductive substance with a terminal engaging member, suchas a drum flange or drum gear for rotating the photosensitive drum(hereinafter simply called a "flange" or "gear") engaged with the endsby bonding with an adhesive or by force fitting under an externalpressure.

The engagement by bonding has been effected by applying an appropriateamount of adhesive onto a part of the gear or flange to be inserted intothe cylinder and, after the fitting, causing the adhesive to becompletely cured while keeping the fitted members in a place(environment) not affected by a change in temperature or humidity. Forthe adhesive, an instant adhesive, and an adhesive primer together withan anaerobic adhesive, etc., have been generally used selectively inview of the usage, purpose, required strength, etc.

It is a recent trend that the gear or flange is formed integrally byinjection molding of a plastic resin in view of the lightness,productivity and production cost, and various plastic resins are used inconsideration of adhesion with the inner surface of the cylinder, thegear strength given thereby and the friction or rubbing characteristicwith respect to the material constituting the mating gear. Further,regarding the shape of the gear or flange gear, a helical gear has alsobeen adopted as disclosed in U.S. Pat. No. 4,829,335 in addition to anordinary spur gear.

A photosensitive drum in an electrophotographic image forming apparatusis generally supported by a position-determining member of the apparatusmain body, but it is necessary to provide a slight clearance orallowance between the main body and the photosensitive drum.Accordingly, in case where the gear is a spur gear, the photosensitivedrum under rotation can cause a positional deviation in the axialdirection so that it is liable to fail in providing good quality ofimages due to a positional deviation of the photosensitive drum duringimage formation. In contrast thereto, if the gear is constituted as ahelical gear, the drum gear under rotation is supplied with a thrust inthe axial direction so that the photosensitive drum is always pushedagainst a constant side and an unstable positional deviation of thephotosensitive drum is obviated.

However, several difficulties as mentioned below have been encounteredwith respect to conventional photosensitive drums as described above.

(1) In the case of a helical gear, an axial thrust is exerted upon aphotosensitive drum under rotation. Accordingly, the helical gear issupplied with an impacting load in the thrust direction, so that theconnection between the drum and the helical gear should be formed asdurable against such repetitive impacting load. This has providedseveral constraints on the selection of adhesives or conditions forforce fitting, and the constraints have resulted in complication of theassembling step and increased production cost.

(2) In case where the bonding and curing are effected in a hightemperature--high humidity environment (e.g., temperature: 32.5° C.relative humidity: 85%), moisture in the atmosphere adversely affectsthe bonding surface to result in a low torque strength.

(3) Very long time is required until the complete curing of an adhesivedepending on the kind of the adhesive used, so that a large space isrequired for the storage during the curing time and a facility forkeeping the temperature and humidity of the storage is also required.Thus, several inconveniences are encountered also in respects of cost,management end productivity.

(4) In order to obtain a high bonding strength, materials of gear andflanges are restricted.

(5) In case where an electrical continuity with an apparatus body istaken by providing the gear or flange end with an electrode platecontacting the inner surface of the cylinder, flagging or flowing theadhesive can occur before the complete curing to cause a conductionfailure between the electrode plate and the inner surface of thecylinder.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of fasteningan engaging member to an end of a cylinder to provide a sufficientfastening or engaging force.

Another object of the present invention is to provide a fastening methodcapable of providing a secure fastening between a cylinder and anengaging member under variable environmental conditions.

A further object of the present invention is to provide a fasteningmethod capable of providing further improved quality of images.

Another object of the present invention is to provide a fastening methodaffording a much improved productivity.

A further object of the present invention is to provide a fasteningmethod capable of realizing a joint with a high accuracy.

According to the present invention, there is provided a method offastening an engaging member to an end of a cylinder, comprising:

processing an inner surface of the cylinder to provide the cylinder witha reduced thickness providing an engaging member having a plurality ofdiscrete recesses formed circumferentially around the periphery of theengaging member, fitting the engaging member into the processed open endof the cylinder and bending and cutting the processed open end of thecylinder at the positions spaced circumferentially around the open endof the cylinder, such that plural parts projected to the recess of theengaging member thereby restricting relative movement between thecylinder and the engaging member in longitudinal and rotationaldirections

According to another aspect of the present invention, there is provideda method of assembling a drum equipped with a helical gear comprising:

providing a cylinder having an outer surface coated with animage-bearing layer,

providing a helical gear having a head to be inserted into an end of thecylinder and a plurality of recesses adjacent to the head,

fitting the helical gear to at least one end of the cylinder, and

bending and cutting the cylinder, at plural parts thereof, into therecesses of the helical gear, thereby fastening the helical gear to atleast one end of the cylinder.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a photosensitive drum according to anembodiment of the present invention.

FIG. 2 is a sectional illustration of a bending and cutting step, andFIG. 3 is a corresponding top plan view, according to an embodiment ofthe invention.

FIG. 4A-4D are sectional views each showing a circular section exampleof a terminal engaging member engaged with a photosensitive drumaccording to an embodiment of the present invention.

FIG. 5 is a sectional view for illustrating sizes involved in thebending and cutting step, and FIG. 6 is a sectional view forillustrating the sizes of a recess of the terminal engaging member (gearor flange), respectively, according to an embodiment of the invention.

FIG. 7 is an illustration of an arrangement of an ordinary transfer-typeelectrophotographic apparatus using a photosensitive drum according toan embodiment of the present invention.

FIG. 8 is a block diagram of a facsimile apparatus including anelectrophotographic apparatus equipped with a photosensitive drumaccording to an embodiment of the present invention as a printer.

FIG. 9 is a partial sectional view of a developing sleeve according toan embodiment of the invention.

FIG. 10 is a sectional illustration of a cylinder and in a bending andcutting step, and FIG. 11 is a corresponding to plan view, according toan embodiment of the invention,

FIG. 12 is a sectional view for illustrating sizes involved in thebending and cutting step, and FIG. 13 is a sectional view forillustrating the sizes of a recess formed in a flange, according to anembodiment of the invention.

FIG. 14 is a side sectional view of a process cartridge according to anembodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment for fastening an engaging member to an end of acylinder according to the present invention will now be described.

The cylinder may preferably have an end brim section having a thicknessof 0.3-1.5 mm, particularly 0.5-1.5 mm. The cut length of the end brimduring the bending and cutting step may preferably be at least 0.2 mm,particularly at least 0.25 mm. This point will be explained in furtherdetail hereinafter.

The cylindrical structure according to the present invention mayeffectively be used as various image bearing members inclusive of aphotosensitive drum, first of all, and also as various roller memberssuch as a platen roller, a conveying roller, a developing sleeve, afixing roller and a printing plate roller, to which a driving force istransmitted and which therefore require a strong engagement between acylinder and a terminal engaging member constituting the same.

The photosensitive drum, i.e., a photosensitive member in a cylindricalform, for electrophotography may take various forms so as to attaindesired characteristics or depending on the kinds of electrophotographicprocesses applied thereto. Representative photosensitive members forelectrophotography may include a photosensitive drum comprising aphotoconductive layer formed on a cylindrical support and aphotosensitive drum further including a surface protective layer thereonwhich have been widely used. The photosensitive drum comprising acylindrical support and a photoconductive layer may be used for imageformation by the most popular electrophotographic process includingcharging, imagewise exposure, development and further transfer asdesired. As for the photosensitive drum provided with a protectivelayer, such a protective layer may be provided for the purpose of, e.g.,protecting the photoconductive layer, improving the mechanical strengthof the photosensitive member, improving the dark decay characteristic,or providing a characteristic suited for a certain electrophotographicprocess.

Some other representative image forming processes, in which cylindricalimage-bearing members may be used, are described below.

(1) In order to improve the repetitive usability of anelectrophotographic photosensitive member, an electrostatic image formedon the electrophotographic photosensitive member is transferred toanother image-bearing member for development, and the resultant tonerimage is transferred to a recording member. (2) In anotherelectrophotographic process involving forming an electrostatic image onanother image-bearing member corresponding to an electrostatic imageformed on an electrophotographic photosensitive member, an electrostaticimage is formed on an electrophotographic photosensitive member in theform of a screen having a large number of minute openings through aprescribed electrophotographic process, a corona charging treatment isapplied to another image-bearing member by the medium of theelectrostatic image to modulate the corona ion stream thereby forming anelectrostatic image on the above-mentioned another image-bearing member,and the electrostatic image is developed with a toner and transferred toa recording member to form a final image. (3) According to anotherelectro-photographic process, a toner image formed on anelectrophotographic photosensitive member or another image-bearingmember is not directly transferred to a recording member but is oncetransferred to still another image-bearing member, and the toner imageis then transferred to a recording member to be fixed thereon. Thisprocess is particularly effective for production of color images andhigh-speed copying. The recording member may ordinarily be a flexiblematerial, such as paper or film. Accordingly, rather than transferringthree color images to a recording member with precise positionalalignment, a more accurately aligned color image can be formed if threecolor images are transferred onto an image-bearing member composed of amaterial substantially free from deformation and then transferred to arecording member at a time. Further, the transfer of a toner image to arecording member by the medium of an image-bearing member is alsoeffective for high-speed copying. (4) In another process, an electricsignal is applied to a multi-stylus electrode to form an electrostaticimage on an image-bearing member corresponding to the electric signal,and the electrostatic image is developed to provide an image.

The image-bearing members used in electrostatic image-forming processlike those of (1)-(4) above do not require a photoconductive layer.

Thus, cylindrical image-bearing members on which electrostatic images ortoner images are formed may comprise various members which may generallyhave an insulating layer as the surface layer, including as arepresentative example an electrophotographic photosensitive memberhaving a surface layer which may be a protective layer or aphotoconductive layer.

The cylindrical structure according to the present invention may forexample be prepared in the following manner. A head (i.e., a part to beinserted into a cylinder) of a terminal engaging member is inserted intoa cylinder of, e.g., aluminum, copper or stainless steel. Adjacent thehead is disposed a recess toward the inside or axis of the terminalengaging member. The recess may have an appropriate shape (inclusive ofwidth, length and depth). To an end brim part covering the recess of thecylinder, a generally claw- or wedge-shaped thrusting member having atip forming an acute angle and having a width almost identical to therecess is abutted and pushed toward the inside of the recess in acertain amount of penetration, whereby the cylinder end brim is bent andsheared almost simultaneously in a shape conforming with the recess. Thesheared part of the bent and cut end brim is intimately attached to andfitted with the recess contour, and the bent and cut part (particularlythe inner surface thereof) of the end brim is intimately attached to theside and bottom of the recess, whereby a reliable fastening is secured.

Hereinbelow, the present invention will be explained based on anembodiment wherein the cylindrical structure is constituted as aphotosensitive drum with reference to drawings. FIG. 1 is a sectionalview of a photosensitive drum according to an embodiment of the presentinvention Referring to FIG. 1, the photosensitive drum includes aterminal engaging member 1, in the form of a helical gear or a flangeequipped with a helical gear, which is engaged with the ends of thephotosensitive drum for rotatably supporting the photosensitive drum andprovided with recesses 2, and a cylinder (cylindrical substrate) 3 ofaluminum alloy surface-coated with a photoconductive layer 5 of aphotosensitive material. The cylinder 3 is fitted about the gear orflange 1 with a certain fitting allowance and engaged with the gear orflange 1 at the recesses 2. The gear or flange 1 may be regarded ascomprising a head (part to be inserted into the cylinder) 1a, a base 1band recesses 2 formed between the head 1a and the base 1b. The helicalgear 1 is rotated about a drum axis 9 by being engaged with a helicalgear 6 driven by a motor (not shown) of the image forming apparatus mainbody for driving the drum supported by a drum-supporting andposition-determining pin 8 fixed to a side wall 7 of the apparatus mainbody 100. Incidentally, the flange equipped with a helical gear maycomprise an insulating plastic.

Referring to FIG. 1, when the drum-driving gear 6 is driven, a thrustfor moving the drum cylinder 3 rightward (in the direction of an arrow)and the drum cylinder 3 is moved rightward. As a result, the end face ofthe helical gear 1 is abutted against the side wall 7 constituting astandard surface of the main body, so that the drum cylinder 3 and thusthe photosensitive drum) is always held at its normal position.

Incidentally, in case where the drum cylinder 3 has an outer diameter ofabout 25-40 mm, it has been experimentally found optimum that the drumgear 1 has a helical Sear with a module of around 0.8 and a twist angleof around 10-20 degrees in view of a relationship between the thrust andthe degree of rubbing between the drum gear 1 and the side wall 7. In aspecific example, the drum cylinder outer diameter was 30 mm, and thedrum gear was designed to have a module of 0.8 and a rightward twistangle of 10 degrees. Another suitable combination may include a cylinderouter diameter of 24 mm and a drum gear 1 having a module of 0.8 and aleftward twist angle of 16 degrees, or a drum cylinder outer diameter of30 mm and a drum gear 1 having a module of 0.9 and a leftward twistangle of 20 degrees.

FIGS. 2 and 3 are a sectional view and a corresponding top plan view,respectively for illustrating the bending and cutting of a cylinder endbrim For this purpose, a thrusting member 4 is abutted to and pushedagainst an end brim of the drum cylinder 3 after the gear or flange 1 isfitted into the cylinder 3 so as to thrust the end brim into the recess2 of the gear or flange 1 while bending and shearing the brim.

The cylinder 3 is fitted about the outer periphery of the head 1aof thegear or flange 1. The fitting at this stage should preferably be not tooloose as to allow relative movement between both members but free fromdeformation of the outer surface of the cylinder 3 brim. Morespecifically, a clearance of 0-10 μm is preferred between the gear orflange and the cylinder 3. Then, after the gear or flange 1 and thecylinder 3 are fitted with each other, a claw- or wedge-shaped thrustingmember 4 having a tip of an acute angle is abutted against the outerperiphery of the cylinder 3 at four parts around the head 1a of the gearor flange 1 as shown in FIG. 3. At this time, as shown in FIG. 2, eachof the four thrusting members 4 is disposed at the same height as thelower end of the cylinder 3, and the tip thereof having a widthidentical to the width of the recess 2 is disposed in horizontalalignment with an associated one of the recesses 2 of the gear or flange1 fitted into the cylinder 3 as shown in FIG. 3 and is then linearlymoved along its axis for abutting. Then, after the abutting, eachthrusting member 4 is caused to go forward with a certain penetrationtoward the axis of the gear or flange 1, whereby the end brim is bentfrom its very lower end along the surface shape of the thrusting member4 and, on further penetration, the end brim is sheared at partsCorresponding to the widths of the recesses 2. As a result, cut and bentparts 3a of the end brim are intimately attached and fixed in therecesses 2, so that the gear or flange 1 and the cylinder 3 are securelyfastened to each other.

At this time, the bent and cut part 3a of the end brim is intimatelyfastened to the recess 2 so that a high engaging force is exhibitedwithout allowing relative movement or loosening between the cylinder 3and the gear or flange 1 in the directions of the rotation and axis ofthe photosensitive drum. The recess 2 may be forced at an arbitraryplurality of parts. e.g., 2 parts, 3 parts, 4 parts, 8 parts or evenmore parts, preferably rotation-symmetrically with respect to the axisof the gear or flange 1 as shown in FIG. 4 for example.

The end peripheral section of the cylinder 3 subjected to the bendingand cutting may desirably be exposed, i.e., free from coating of aphotosensitive substance for a length of at least 1.0 mm, preferably atleast 5.0 mm, from the very end in the longitudinal direction of thecylinder 3. The coating-free end section length should not beexcessively large since at can decrease the image forming area formed bythe coated area.

The sizes involved in the bending and cutting step will now be describedwith reference to FIG. 5. Referring to FIG. 5, the thrusting member 4 isallowed to enter for a penetration a toward inside the cylinder from theposition where it just contacts the outer periphery of the cylinder 3.By adjusting the penetration a, it is possible to control the fasteningforce between the gear or flange 1 and the cylinder 3. The cylinder 3has a thickness b and may ordinarily comprise a drawn pipe of analuminum-based metal. In specific examples described hereinafter, analuminum-based drawn pipe ("H63S" (trade name) available from Kobe SeikoK.K.) having a thickness b of 0.7 mm (outer diameter: 29.92 mm, innerdiameter: 28.50 mm) and a length of 260.5 mm was used. A largerthickness b provides a larger fastening torque strength, but too large athickness b requires a very large force for bending and cutting by thethrusting member 4, thus adversely affecting size accuracy of thesurrounding parts. For this reason, a thickness b of 0.3-1.5 mm,particularly 0.6-1.0 mm, is preferred for sizes of a cylinder asdescribed above. The thrusting member 4 may have tip angle e which maybe arbitrarily set in consideration of its shape, etc., but basically anacute angle, preferably in the range of 10-70 degrees, more preferably20-40 degrees. Incidentally, in the examples appearing hereinafter, aclaw- or wedge-shaped thrusting member having smooth surfaces, a tipangle of 30 degrees and a width of 3 mm was used.

The end brim of the cylinder 3 is cut in a length of f. A larger cutlength f provides a larger fastening force. The cut length f may dependon the penetration a and may preferably be at least 0.2 mm, particularlyat least 0.4 mm. However, the length need not exceed 3 mm.

FIG. 6 illustrates sizes of the recess 2 formed in the gear or flange 1.More specifically, the recess 2 has a width (peripheral length in adirection transverse to the axis of the gear of flange 1) c, and aheight (length in the direction of the axis of the gear or flange 1) d.These sizes of the recess 2 may be set to appropriate values dependingon the outer diameter and the thickness of the drum cylinder 3. For theabove-described sizes of the cylinder, for example, the width c maydesirably be at least 1 mm, and the height d may desirable be at least0.5 mm. The shape of the recess 2 is not limited to a rectangular onebut may be circular, arc (partial circle), triangular, etc. The shapeand size of the recess can be changed depending on the shape and outerdiameter of the gear or flange 1, and the tip shape of the thrustingmember 4 can be changed correspondingly.

The cut and bent part of the cylinder end brim may preferably have awidth which is in the range of 0.95-1 times the width of the recess 2,particularly identical to the width of the recess

FIG. 7 shows an outline of an ordinary transfer-type electrophotographicapparatus including a photosensitive drum according to the presentinvention.

Referring to FIG. 7, the apparatus includes a photosensitive drum 101 asan image-bearing member which rotates about an axis 101a at a describedperipheral speed in the direction of the arrow, the course of therotation, the peripheral surface of the photosensitive drum 101 isuniformly charged to a positive or negative prescribed potential by acharging means 102 and then exposed to image light L by an imagewiseexposure means (not shown, such as slit exposure means or laser beamscanning exposure means) at an exposure position 103. As a result, anelectrostatic latent image corresponding to the exposure light image issequentially formed on the peripheral surface of the photosensitive drum101.

The electrostatic latent image is then developed with atoner by adeveloping means 104 including a developing sleeve 104a, and theresultant toner image is sequentially transferred by a transfer means105 onto a transfer material or paper P which has been supplied betweenthe photosensitive member 101 end the transfer means 105 in synchronismwith the rotation of the photosensitive member 101 by a paper-supplyingmeans including pairs of rollers 109. Herein, it is also possible toform the developing sleeve 104a as a cylindrical structure according tothe present invention.

The transfer material P having received the toner image is separatedfrom the photosensitive member surface and introduced to an image fixingmeans 108 for image fixation to be discharged as a copy product out ofthe apparatus.

The surface of the photosensitive member 101 after the image transfer issubjected to removal of transfer-residual toner by a cleaning means 106to be cleaned, discharged by a pre-exposure means 107, and used forrepetitive image formation.

A corona charging device is widely used in general as the uniformcharging means 102 for the photosensitive member 101. A corona transfermeans is also widely used in general as the transfer means 105.

In the electrophotographic apparatus, plural members including some ofthe above-mentioned photosensitive member 101, developing means 104,cleaning means 106, etc., can be integrally combined to form anapparatus unit so that the unit can be readily connected to or releasedfrom the apparatus body. For example, the photosensitive member 101 andthe cleaning means 106 can be integrated into a single unit so that itcan be attached to or released from the apparatus body by a guide meanssuch as a guide rail provided to the apparatus body. In this instance,the apparatus unit can also be integrally accompanied with the chargingmeans 102 and/or the developing means 104.

In a case where the electrophotographic apparatus is used as a copyingmachine or a printer, the image light L is a reflected light ortransmitted light from an original, or an image light formed by codingread data from an original and scanning a laser beam or driving alight-emitting diode array or a liquid crystal shutter array based onthe coded data,

In a case where the image forming apparatus is used as a printer forfacsimile, the image light L may be replaced by exposure light image forprinting received data. FIG. 8 is a block diagram for illustrating suchan embodiment.

Referring to FIG. 8, a controller 111 controls an image reader (or imagereading unit) 110 and a printer 119. The entirety of the controller 111is regulated by a CPU 117. Data read from the image reader 110 istransmitted through a transmitter circuit 113 to a remote terminal suchas another facsimile machine. On the other hand, data received from aremote terminal is transmitted through a receiver circuit 112 to aprinter 119. An image memory 116 stores prescribed image data. A printercontroller 118 controls the printer 119. A telephone handset 114 isconnected to the receiver circuit 112 and the transmitter circuit 113.

More specifically, an image received from a line (or circuit) 115 (i.e.,image data received from a remote terminal connected by the line) isdemodulated by means of the receiver circuit 112, decoded by the CPU117, and sequentially stored In the image memory 116. When image datacorresponding to at least one page is stored in the image memory 116,image recording or output is effected with respect to the correspondingpage. The CPU 117 reads image data corresponding to one page from theimage memory 116, and transmits the decoded data corresponding to onepage to the printer controller 118. When the printer controller 118receives the image data corresponding to one page from the CPU 117, theprinter controller 118 controls the printer 119 so that image datarecording corresponding to the page is effected. During the recording bythe printer 119, the CPU 117 receives another image data correspondingto the next page.

Thus, receiving and recording of an image may be effected in theabove-described manner by using an electrophotographic apparatusequipped with an image-bearing member according to the present inventionas a printer.

EXAMPLE 1

A photosensitive drum as shown in FIG. 1 was prepared through a processas explained with reference to FIGS. 1-6 above.

An aluminum-made drawn cylinder or tube ("H63S" (trade name) availablefrom Kobe Seiko K.K.; inner diameter 28.50 mm and thickness of 0.7 mmrespectively at the fitting ends; length: 260.5 mm) was coated bydipping with an ammoniacal aqueous solution of casein (casein 11.2 g,28%-ammonia water 1 g, water 222 ml), followed by drying to form aprimer layer at a rate of 1.0 g/m².

Then, 1 wt. part of aluminum chloride phthalocyanine, 1 wt. part ofbutyral resin ("Eslec BM-2" (trade name), available from Sekisui KagakuK.K.) and 30 wt. parts of isopropyl alcohol were dispersed for 4 hoursin a ball mill. The resultant dispersion was applied by dipping onto theabove-prepared primer layer and dried to form a 0.3 μm-thick chargegeneration layer.

Separately, 1 wt. part of a hydrazone compound, 1 wt. part ofpolysulfone resin ("P1700" (trade name) available from Union CarbideCo.) and 6 wt. parts of monochlorobenzene were mixed under stirring. Theresultant liquid was applied onto the charge generation layer by dippingand dried to form a 12 μm-thick charge transport layer, thus providing acoated drum cylinder 3 as shown in FIG. 1 in a state before bending.

Separately, a drum helical gear 1 (a module of 0.8 and a rightward twistangle of 10 degrees) was formed from polyacetal copolymer resin("Duracon M90-02" (trade name) available from Polyplastic K.K.) byinjection molding (under the conditions of nozzle temp.: 200° C.,cylinder temp.: tip: 180° C., medium: 170° C., rear: 160° C.; moldtemp.: cavity: 60° C., core: 60° C.) to have a head (inserted part)outer diameter of 28.49 mm and four rectangular recesses (width: 3 mm,height: 1.5 mm, depth: 3 mm) at 4 parts adjacent to the head anddisposed at right angles from the axis of the gear 1.

To the gear 1 thus obtained, the above-prepared drum cylinder 3 wasfitted so as to cover the head 1a of the gear 1 with its lower end brim,and four thrusting members 4 were caused to contact the outer surface ofthe lower end brim of the cylinder 3 as shown in FIG. 3. Each thrustingmember 4 had a tip having a width of 3 mm and an angle (e) of 30 degreesand formed of SKD 30. After the contact, the thrusting members 4 werefurther pushed against the cylinder end brim at a penetration of 2.5 mmto bend and shear the end brim so as to conform to the shape of therecesses 2. The cut length of the cylinder end brim was 1.4 mm. Thus,the gear 1 was fastened to one end of the drum cylinder. Another gearwas similarly fastened to the other end of the drum cylinder.

The thus obtained photosensitive drum was loaded in a process cartridgefor a laser beam printer ("LBP-SX" (trade name) available from CanonK.K.) and the process cartridge was left standing for 48 hours in anenvironment of high temperature--high humidity (32.5° C.-85% RH). Then,the process cartridge was loaded in the laser beam printer and subjectedto an image forming test of 10000 sheets. During the test, good imageswere obtained without occurrence of irregularities, such as pitchirregularities or fog, which might be attributable to the photosensitivedrum. After the image forming test, the photosensitive drum was takenout of the cartridge to examine whether any defects, such as play,loosening and dislocation, occurred at the joint between the gear andthe cylinder, no defects in these respects were observed at all.Further, during the continuous image forming test, no noise was causeddue to friction of the drum gear so that a smooth rotation of the drumgear was confirmed.

Further, as a result of image quality evaluation of halftone images,very good images were obtained free from drum gear pitch irregularity.

Finally, the photosensitive drum after the image forming test was fixedand subjected to measurement of a rupture torque at the joint by meansof a commercially available torque gauge, whereby the rupture was causedat a torque of 160 kg-cm, which is sufficiently large from a practicalviewpoint.

EXAMPLE 2

A photosensitive drum was prepared in the same manner as in Example 1except that the thrusting member after the contact was further pushed tocause a penetration of 2.0 mm. The cut length at the sheared part of thecylinder end brim was 1.10 mm. The resultant photosensitive drum wasevaluated in the same manner as in Example 1, whereby similar resultswere obtained. The rupture torque of the photosensitive drum at thejoint after the image forming test was 145 kg-cm.

EXAMPLE 3

A photosensitive drum was prepared in the same manner as in Example 1except that the penetration of the thrusting member after the contactwas changed to 1.5 mm. The cut length at the sheared part of thecylinder end brim was 0.85 mm. The resultant photosensitive drum wasevaluated in the same manner as in Example 1, whereby similar resultswere obtained. The rupture torque of the photosensitive drum at thejoint after the image forming test was 122 kg-cm.

EXAMPLE 4

A photosensitive drum was prepared in the same manner as in Example 1except that the penetration of the thrusting member after the contactwas changed to 1.0 mm. The cut length at the sheared part of thecylinder end brim was 0.55 mm. The resultant photosensitive drum wasevaluated in the same manner as in Example 1, whereby similar resultswere obtained. The rupture torque of the photosensitive drum at thejoint after the image forming test was 70 kg-cm.

COMPARATIVE EXAMPLE 1

A drum gear and a drum cylinder prepared in the same manner as inExample were bonded to each other with 0.08 g of an instant adhesive("ARONALPHA 432FTW" (trade name) available from Toa Gosei Kagaku KogyoK.K. and left standing for 48 hours in an environment of 32.5° C. and85% RH for complete curing. The resultant photosensitive drum wasevaluated in the same manner as in Example 1, whereby the gear wasdislocated after about 500 sheets of image formation. The part of thebonding failure was observed to be caused as an interfacial breakage atthe boundary between the drum gear and the adhesive. The rupture torqueat this time was 55 kg-cm.

COMPARATIVE EXAMPLE 2

A drum cylinder and a drum gear prepared in the same manner as inExample 1 were fastened with each other in a similar manner as inExample 1 except that the thrusting member after contacting theperiphery of the cylinder was further pushed to cause a penetration ofonly 0.5 mm whereby the gear was engaged with the cylinder only bystaking. i.e. without causing cutting, of the cylinder.

The thus prepared cylinder was evaluated in the same manner as inExample 1 whereby a play of about 0.5 mm occurred in the rotationaldirection at the time of 6000 sheets during the durability test. Afterthe durability test, the joint between the photosensitive drum and thedrum gear was observed, whereby the stated part of the cylinder was notsheared but a gap was found with the recess. The rupture torque at thistime was 62 kg-cm.

The above-mentioned results of Examples and Comparative Examples aresummarized in the following Table 1.

                                      TABLE 1                                     __________________________________________________________________________    Shape               Cut          Image  Rupture                               of gear  Manner of                                                                          Penetration                                                                         length                                                                            Number of copied                                                                       evalua-                                                                              torque                                teeth    fastening                                                                          (mm)  (mm)                                                                              sheets, results                                                                        tion                                                                              Noise                                                                            (kg-cm)                               __________________________________________________________________________    Example 1                                                                          helical                                                                           bending &                                                                          2.5   1.40                                                                              1000 sheets, no play                                                                   good                                                                              good                                                                             160                                            cutting        or loosening                                          Example 2                                                                          "   bending &                                                                          2.0   1.10                                                                              1000 sheets, no play                                                                   "   "  145                                            cutting        or loosening                                          Example 3                                                                          "   bending &                                                                          1.5   0.85                                                                              1000 sheets, no play                                                                   "   "  122                                            cutting        or loosening                                          Example 4                                                                          "   bending &                                                                          1.0   0.55                                                                              1000 sheets, no play                                                                   "   "   70                                            cutting        or loosening                                          Comp.                                                                              helical                                                                           bonding                                                                            --    --  Gear disclosed at                                                                      good                                                                              good                                                                              55                                   Example 1               5000 sheets                                           Comp.                                                                              "   shaking                                                                            0.5   0   Play of 0.5 mm at                                                                      good                                                                              good                                                                             62                                    Example 2               6000 sheets                                           __________________________________________________________________________

As described above, the cylindrical structure obtained according to thisembodiment has the following advantageous features.

(1) A terminal engaging member having a helical gear is fastened to atleast one end of a cylinder so as exert a thrust for pushing thecylindrical structure in its axial direction, whereby a photosensitivedrum including the cylindrical structure is always rotated at a normalposition free from a positional deviation in the axial direction, thusstably providing high-quality images.

(2) The helical gear in the terminal engaging member having obliqueteeth provides a larger rate of engagement than a spur gear and causelittle vibration due to gear engagement, so that a smooth rotation ofthe terminal engaging member is obtained to cause little noise duringthe drive.

(3) In the cylindrical structure, the end brim of the cylinder is bentand cut into recesses adjacent to the head of the terminal engagingmember inserted into the cylinder so that the cut and bent brim iscaused to be intimately fastened to the engaging member. As a result,the resultant fastened structure can always show a stable engagementforce without being affected by external factors under variousenvironmental conditions (ranging from low temperature--low humidity tohigh temperature--high humidity). Further, a strong engagement force asrepresented by a torque strength comparable to even higher than thoseobtained by conventional method of fastening as by adhesion or forcefitting can be obtained by a simple production step. The resultant jointstructure is so stable that the fastened drum gear is not out ofposition even under application of a repetitive impact force in theaxial direction due to the use of a helical gear.

(4) The engagement or fastening between the terminal engaging member andthe cylinder can be effected by a simple method of pressing a thrustingor protruding member from an outer periphery of the cylinder.Accordingly, a complete curing time as required in the conventionalbonding method is not required but the engagement can be performedinstantaneously, thus being advantageous in reelects of productivity andproduction cost.

(5) Further, as no adhesive is required, it is not required to exercisethe control of the property of the adhesive or employ the drying stepand storage space after the bonding.

(6) Further, the engagement torque strength is not affected by thematerial of the terminal engaging member, so that the material thereofcan be freely selected in view of its purpose and usage.

(7) In the cylindrical structure, the cylinder and the terminal engagingmember are fastened with each other at a strong engaging force. Thestrong engaging force is given by bending and cutting the end brim ofthe cylinder into the recess of the terminal engaging member adjacent tothe head inserted into the cylinder. This is because, by bendingaccompanied with cutting, instead of simple bending, of the end brim ofthe cylinder, the bent and cut end brim is caused to intimately enterthe recess of the terminal engaging member. The bending and cutting ofthe cylinder end brim can be easily performed by using a wedge- orclaw-shaped thrusting member.

It is possible to apply the embodiment described with reference to FIGS.1-7 to a developing sleeve as will be described with reference to FIGS.9-13.

Now, an embodiment of using a cylinder having an inner surface processedfor socket joint in order to provide a further improved accuracy ofjoint or fastening will be described with reference to FIGS. 9-13 basedon application to a developing sleeve as an example of the cylindricalstructure. This embodiment is of course applicable to a photosensitivedrum as described in the previous embodiment. It is also possible tocombine the previous embodiment and the following embodiment in order toform a cylindrical structure, e.g., for fastening a terminal engagingmember equipped with a helical gear to a photosensitive drum cylinderhaving an inner surface processed for socket joint.

First of all, a developing apparatus using a developing sleeve will bedescribed.

In an image forming apparatus using electrophotography, etc., it hasbeen practiced to develop an electrostatic image formed on aphotosensitive drum with a developer to form a toner image as a visibleimage. As a type of such a developing apparatus, there has been knownone wherein a one-component type developer comprising a magnetic toneris used.

In such a developing apparatus using a one-component type developercomprising a magnetic toner, the developer is provided with an electriccharge of a polarity opposite to that of an electrostatic image on aphotosensitive drum by friction between developer particles and alsobetween the developer and a developing sleeve. The developer thusprovided with an opposite polarity charge is regulated by a developerregulating member to form a thin layer of the developer which is thenconveyed to a developing position under the action of a magnetic fieldgiven by a fixed magnet within the developing sleeve. At the developingposition, the developer is caused to fly and be attached onto theelectrostatic image on the photosensitive drum to develop theelectrostatic image as a toner image.

As is disclosed in, e.g., JP-A 57-66455, the developing sleeve may beformed by toughening the surface of a cylinder of a metal, such asaluminum, nickel, stainless steel or alloys of these metals, e.g., byelectrolysis., blasting, or filing. The surface may be coated with afilm in a prescribed thickness of a paint comprising, e.g., graphite orcarbon black, a phenolic resin and isopropyl alcohol (JPA) in mixtureand dispersion and air-sprayed onto the cylinder surface. Finally,flanges are fastened to the cylinder ends to assemble a developingsleeve.

As described above, such a developing sleeve is disposed opposite to thephotosensitive drum and is rotated by a driving force supplied by gearengagement to provide the developer with a charge and convey thedeveloper to the developing position, so that the developing sleeve isrequired to show mechanical properties, such as uniform and smoothrotation characteristic, mechanical strength in resistance to therotation torque exerted thereby and stability under variousenvironmental conditions.

Now, production of a developing sleeve, for example, according to thisembodiment will be described with reference to FIGS. 9-11.

Similarly as in the previous embodiment, the cylinder 33 may preferablyhave an end brim section having a thickness of 0.3-1.5mm, particularly0.5-1.5 mm. The cut length of a bent and cut portion of the cylinder endbrim may preferably be at least 0.2 mm, particularly at least 0.25 mm.

In this embodiment, the cylinder 33 comprising aluminum, copper,stainless steel, etc., provided with an end brim section B where thecylinder inner surface is processed to improve the inner diameteraccuracy, e.g., by machining, such as cutting, abrading or grinding, inorder to improve the fitting accuracy with an engaging member.

Into this inner surface-processed section B of the cylinder 33, a head31a of a flange 31 of, e.g., an insulating plastic is lightlypress-fitted. In or adjacent to the head 31a, the flange 31 is providedwith recesses 32 of appropriate dimensions, such as width, length anddepth. To and end brim part of the cylinder, a generally claw-orwedge-shaped thrusting member 34 having a tip forming an acute angle anda width almost equal to the recess 32 is abutted and pushed toward theinside of the recess 32 in a certain amount of penetration, whereby thecylinder end brim is bent and sheared simultaneously in a shapeconforming with the recess 32. The sheared part of the bent and cut endbrim is intimately attached to and fitted with the recess con, our, andthe bent and cut part 33a (particularly the inner surface thereof) ofthe end brim is intimately attached to the side and bottom of therecess, whereby a reliable fastening is secured.

Hereinbelow, the details of this embodiment will be described withreference to drawings. FIG. 9 is a sectional view of a developing sleeveaccording to this embodiment. Referring to FIG. 9, the developing sleeveincludes a flange 31 as a terminal engaging member engaged with the endsof the developing sleeve for rotatably supporting the photosensitivedrum and provided with recesses 32, and a cylinder (cylindricalsubstrate) 33 of aluminum alloy. The inner surface of the fittingportion B of the cylinder 33 is processed by cutting, abrading orgrinding for press-fitting with the flange head at a press fit margin (asubtraction of the cylinder inner diameter at the processed portion Bfrom the outer diameter of the flange head 31 before insertion) of 5-180μm. The press fit margin may be determined arbitrarily within an extentof not adversely affecting the function of the developing sleeve whileit can depend on the materials of the flange 31 and the cylinder 33, andthe fitting length. In a sense, the inner surface-processing of thecylinder end brim has a function of thinning the end brim portion so asto be suitable for bending-and-cutting and for light press fitting withthe head while retaining the mechanical strength of the entire cylinder.

FIGS. 10 and 11 are a sectional view and a corresponding top plan view,respectively, for illustrating the bending and cutting of a cylinder endbrim. For this purpose, a thrusting member 34 is abutted to and pushedagainst an end brim of the sleeve cylinder 33 after the flange 31 isfitted into the cylinder 33 so as to thrust the end brim into the recess32 of the flange 31 while bending and shearing the brim.

The inner surface-processed part B of the cylinder 33 is fitted aboutthe outer periphery of the head 31a of the flange 31. The fitting atthis stage should preferably be light-press fitting with a press fitmargin of preferably 5-180 μm, more preferably 5-100 μm, furtherpreferably 5-50 μm.

Then, after the flange 31 and the cylinder 33 are fitted with eachother, a claw- or wedge-shaped thrusting member 34 having a tip of anacute angle is abutted against the outer periphery of the cylinder 33 atfour parts around the head 31a of the flange 31 as shown in FIGS. 10 and11. At this time, as shown in FIG. 10, each of the four thrustingmembers 34 is disposed at the same height as the lower end of thecylinder 33, and the tip thereof having a width identical to the widthof the recess 32 is disposed in horizontal alignment with an associatedone of the recesses 32 of the flange 31 fitted into the cylinder 33 asshown in FIG. 11 and is then linearly moved along its axis for abutting.Then, after the abutting, each thrusting member 34 is caused to goforward with a certain penetration toward the inside of the flange 31,whereby the end brim is bent from its very lower end along the surfaceshape of the thrusting member 34 and, on further penetration, the endbrim is sheared at parts corresponding to the widths of the recesses 32.AS a result, cut and bent parts 33a of the end brim are intimatelyattached and fixed in the recesses 32, so that the flange 31 and thecylinder 33 are securely fastened to each other.

More specifically, the bent and cut part 33a of the end brim isintimately fastened to the recess 32 so that a high engaging force isexhibited without allowing relative movement or loosening between thecylinder 33 and the flange 31 in the directions of the rotation and axisof the developing sleeve. The recess 32 may be formed at an arbitraryplurality of parts, e.g., 2 parts, 3 parts, 4 parts, 8 parts or evenmore parts, preferably rotation-symmetrically with respect to the axisof the flange 31.

The sizes involved in the bending and cutting step will now be describedwith reference to FIG. 12. Referring to FIG. 12, the thrusting member 34is allowed to enter for a penetration a toward inside the cylinder fromthe position where it just contacts the outer periphery of the cylinder33. By adjusting the penetration a, it is possible to control thefastening force between the flange 31 and the cylinder 33. The cylinder33 has a thickness b. A larger thickness b provides a larger fasteningtorque strength, but too large a thickness b requires a very large forcefor bending and cutting by the thrusting member 34, thus adverselyaffecting the size accuracy of the surrounding parts. For this reason, athickness b of 0.3-1.5 mm, particularly 0.6-1.0 mm, is preferred forsizes of a cylinder as described above. The inner surface processingalleviates the above thickness contradiction regarding the strength andthe easiness of cutting and bending. The thrusting member 34 may have atip angle e which may be arbitrarily set in consideration of its shape,etc., but basically an acute angle, preferably in the range of 10-70degrees, more preferably 20-40 degrees. Incidentally, in the examplesappearing hereinafter, a claw- or wedge-shaped thrusting member havingsmooth surfaces, a tip axle of 30 degrees and a width of 3 mm was used.

The end brim of the cylinder 33 is cut in a length of f. A larger cutlength f provides a larger fastening force. The cut length f may dependon the penetration a and may preferably be at least 0.2 mm, particularlyat least 0.4 mm.

FIG. 13 illustrates sires of the recess 32 formed in the gear orflange 1. More specifically, the recess 32 has a width (peripherallength In a direction transverse to the axis of the gear of flange 31)c, and a height (length in the direction of the axis of the gear orflange 31) d. These sizes of the recess 32 may be set to appropriatevalues depending on the outer diameter and the thickness of the sleevecylinder 33. For the above-described sizes of the cylinder, for example,the width c may desirably be least 1 mm, and the height d may desirablebe at least 0.5 mm. the shape of the recess 32 is not limited to arectangular one but may be circular, arc (partial circle), triangular,etc. The shape and size of the recess can be changed depending on theshops and outer diameter of the gear or flange 31, and the of thethrusting member 34 can be changed correspondingly.

The cut and bent part of the cylinder end brim may preferably have awidth which is in the range of 0.95-1 times the with of the recess 32,particularly identical to the width of the recess 32.

The developing sleeve 30 according to this embodiment may be applicableto any image forming apparatus utilizing electrophotography, etc., andthe developer used therewith may be any of the known one-component typeand two-component type developers. Further, as one example is shown inFIG. 10, the developing sleeve may be equipped with a helical gear 31b(shown by two dots-and-dash lines) at its end. By using such a helicalgear, a driving force is smoothly transmitted to the sleeve and theposition of the sleeve 30 can be accurately determined.

EXAMPLE 5

An aluminum drawn cylinder 33 (mfd. by Showa Aluminum K.K.; outerdia.=16 mm, inner dia.=14.40 mm, thickness=0.8 mm, length=248 mm) wasinner surface-processed at its end portions of each 10 mm from the veryend with a cut thickness of 0.1 mm (one side).

Then, the outer surface of the cylinder was sand-blasted with alundumparticles by a sand-blasting machine of an ordinary jet air type("Pneumablaster", mfd. by Fuji Seisakusho K.K.) at an ejection pressureof 4 kg/cm² for 60 sec. while rotating the cylinder at 20 rpm. Theresultant sleeve cylinder had an average surface roughness (Ra, counterline average surface roughness according to JIS B-0601) of 3.0 μm.

Then, a paint was prepared by mixing the following composition:

    ______________________________________                                        Phenolic resin     20 wt. part(s)                                             Natural graphite (dav. = 7 μm)                                                                 9 wt. part(s)                                             Carbon black (Dav. = 0.2 μm)                                                                   1 wt. part(s)                                             IPA                20 wt. part(s)                                             ______________________________________                                    

followed by dispersion together with glass beads in a paint shaker for30 min. The paint, after being adjusted to a solid content of 25%, wasair-sprayed onto the sleeve cylinder 33 to form a film, which was thencured under heating at 150° C. for 30 min. in a hot air drying oven. Theresultant coating showed an average surface roughness (Ra) of 2.4 μm.

To both ends of the developing sleeve thus formed, a sleeve flange madeby injection molding of a polyacetal resin ("Duracon AW-01", made byPolyplastic K.K.) was fitted at a press fit margin of 50 μm. The flangewas provided with four rectangular recess 32 (width=3 mm, height=1 mm,and depth=3 mm) at 4 parts adjacent to the head 31a and disposed atright angles from the axis of the flange.

Then, to the end brim of the developing sleeve fitted about the head andrecesses 32 of the flange 31, four thrusting members 34 were abutted atthe positions of the recesses and further pushed at a penetration of 1.5mm against the end brim to bend and cut the brim at a cut length of 0.85mm, whereby the flanges 31 were fastened to the developing sleeve 33.Each thrusting member had a tip width of 3 mm and a tip angle of 30degrees and was made of SKD 30.

The thus obtained developing sleeve 30 was then subjected to a flangeswing test in the following manner in order to evaluate whether theflange 31 and the sleeve cylinder 33 were fastened to each other at ahigh accuracy without being inclined or bent.

The developing sleeve 30 was held in parallel with a master gauge (outerdia.=16 mm, and length=300 mm) with two spacers (cylindrical shape withdia.=8 mm, height=10 mm) disposed at two end parts of the sleeve toprovide their peripheral circular surfaces as contacting surfaces andsandwiched between the developing sleeve and the master gauge. The helddeveloping sleeve and master gauge held in parallel were illuminatedwith laser light incident at right angles from a laser length meter, andthe distance between the flange outer surface and the master gauge wasmeasured while rotating the developing sleeve 30. The difference betweenthe maximum and the minimum values of the distance during one rotationof the developing sleeve was measured as a flange swing which was foundto be 10 μm in this Example as a result of the measurement.

The above-prepared developing sleeve was loaded in a cartridge 50 for alaser beam printer ("LBP-SX", mfd. by Canon K.K.) and left standing for48 hours in an environment of normal temperature--normal humidity (25°C.-40% RH), and then the cartridge was loaded in the laser beam printerin the same environment and subjected to an image forming test of 5000sheets. During the test, good images were obtained without occurrence ofirregularities, such as pitch irregularities or fog, due to thedeveloping sleeve.

EXAMPLES 6-9

Developing sleeves were prepared and tested for image formation in thesame manner as in Example 5 except that the press fit margins werechanged as shown in Table 2 appearing hereinafter. The results are alsoshown in Table 2.

COMPARATIVE EXAMPLE 3

An aluminum drawn cylinder identical to the one used in Example 5 asdrawn and without inner surface processing was sand-blasted andfilm-coated in the same manner as in Example 5.

An instant adhesive ("ARONALPHA 432FTW" (trade name) available from ToaGosei Kagaku Kogyo K.K.) was applied to the fitting portion innersurface of the cylinder, into which a head of a sleeve flange preparedby injection molding of polycarbonate resin ("Yupilon LS2030" (tradename) available from Mitsubishi Gas Kagaku K.K. and containing 15 wt. %of fluorine-containing resin powder) was inserted for fitting with aclearance of 50-60 μm between the flange head outer diameter and thecylinder inner diameter. Then, the structure was left standing for 48hours in an environment of normal temperature--normal humidity (25°C.-40% RH) for complete curing. The thus obtained developing sleeve wasevaluated in the same manner as in Example 5. The results are also shownin the following Table 2.

                  TABLE 2                                                         ______________________________________                                        Manner of     Press fit                                                                              Flange  Pitch   Image                                  fastening     margin   swing   irregularity                                                                          density                                ______________________________________                                        Example 5                                                                            press fitting +                                                                           50 (μm)                                                                            10 (μm)                                                                          ⊚                                                                      ⊚                            bending &                                                                     curring                                                                Example 6                                                                            press fitting +                                                                           80      13    ⊚                                                                      ⊚                            bending &                                                                     curring                                                                Example 7                                                                            press fitting +                                                                          120      15    ⊚                                                                      ⊚                            bending &                                                                     curring                                                                Example 8                                                                            press fitting +                                                                          150      20    ∘                                                                         ∘                               bending &                                                                     curring                                                                Example 9                                                                            press fitting +                                                                          180      24    ∘                                                                         ∘                               bending &                                                                     curring                                                                Comp.  bending    -50      74    x       ∘                        Example 3         (clearance                                                                    fitting)                                                    ______________________________________                                    

The following experiments (Examples 10-13 and Comparative Example 4)were performed regarding the fastening strength between the flange andthe cylinder.

EXAMPLE 10

A developing sleeve was prepared in the same manner as in Example 5except that the penetration of the thrusting member after the contactwas changed to 2.5 mm. The cut length at the sheared part of thecylinder end brim was 1.4 mm. The resultant developing sleeve was loadedin a process cartridge for a laser beam printer ("LBP-SX" (trade name)available from Canon K.K.) and the process cartridge was left standingfor 48 hours in an environment of high temperature--high humidity (32.5°C.-85%RH). Then, the process cartridge was loaded in the laser beamprinter and subjected to an intermittent image forming rest of 10000sheets in the same environment. During the test, good images wereobtained without occurrence of irregularities, such as pitchirregularities or fog, which might be attributable to the developingsleeve. After the image forming test, the developing sleeve was takenout of the cartridge to examine whether any defects, such as play,loosening and dislocation, occurred at the joint between the flange 31and the cylinder 33, occurred. As a result, no defects in these respectswere observed at all. The developing sleeve after the image forming testwas fixed and subjected to measurement of a rupture torque at the jointby means of a commercially available torque gauge, whereby the rupturewas caused at a torque of 70 kg-cm.

EXAMPLE 11

A developing sleeve was prepared in the same manner as in Example 10except that the penetration of the thrusting member after the contactwas changed to 2.0 mm. The cut length at the sheared part of thecylinder end brim was 1.10 mm. The resultant developing sleeve wasevaluated in the same manner as in Example 10, whereby similar resultswere obtained. The rupture torque of the developing sleeve at the jointafter the image forming test was 60 kg-cm.

EXAMPLE 12

A developing sleeve was prepared in the same manner as in Example 10except that the penetration of the thrusting member after the contactwas changed to 1.5 μm. The cut length at the sheared part of thecylinder end brim was 0.85 mm. The resultant developing sleeve wasevaluated in the same manner as in Example 10, whereby similar resultswere obtained. The rupture torque of the developing sleeve at the jointafter the image forming test was 45 kg-cm.

EXAMPLE 13

A developing sleeve was prepared in the same manner as in Example 10except that the penetration of the thrusting member after the contactwas changed to 1.0 mm. The cut length at the sheared part of thecylinder end brim was 1.55 mm. The resultant developing sleeve wasevaluated in the same manner as in Example 10, whereby similar resultswere obtained. The rupture torque of the developing sleeve at the jointafter the image forming test was 35 kg-cm.

COMPARATIVE EXAMPLE 4

A sleeve flange and a sleeve cylinder prepared in the same manner as inComparative Example 3 were bonded to each other with 0.08 g of aninstant adhesive ("ARONALPHA 432FTW" (trade name) available from ToaGosei Kagaku Kogyo K.K. and left standing for 48 hours in an environmentof 32.5° C. and 85% RH for complete curing. The resultant developingsleeve was evaluated in the same manner as in Example 10, whereby theflange was dislocated after about 500 sheets of image formation. Thepart of the bonding failure was observed to be caused as an interfacialbreakage at the boundary between the flange and the adhesive. Therupture torque at this time was 22 kg-cm.

The above-mentioned results of Examples 10-13 and Comparative Example 4are summarized in the following Table 3.

                                      TABLE 3                                     __________________________________________________________________________    Manner of        Cut  Number of copied                                                                        Rupture torque                                fastening  Penetration                                                                         length                                                                             sheets, results                                                                         kg-cm                                         __________________________________________________________________________    Example 10                                                                          bending &                                                                          2.5 mm                                                                              1.40 mm                                                                            10000 sheets, no play                                                                   70                                                  cutting         or loosening                                            Example 11                                                                          bending &                                                                          2.0 mm                                                                              1.10 mm                                                                            10000 sheets, no play                                                                   60                                                  cutting         or loosening                                            Example 12                                                                          bending &                                                                          1.5 mm                                                                              0.85 mm                                                                            10000 sheets, no play                                                                   45                                                  cutting         or loosening                                            Example 13                                                                          bending &                                                                          1.0 mm                                                                              0.55 mm                                                                            10000 sheets, no play                                                                   35                                                  cutting         or loosening                                            Comp. bonding                                                                            --    --   Flange disclosed at                                                                     22                                            Example 4             500 sheets                                              __________________________________________________________________________

As described above, the developing sleeve obtained according to thisembodiment has the following advantageous feature in addition to (3)-(7)described with reference to the previous embodiment of thephotosensitive drum provided with a helical gear after Table 1.

Thus, in the developing sleeve, the flange can be fastened to thecylinder at a high accuracy without being inclined or bent with respectto the cylinder. Accordingly, the occurrence of pitch irregularity dueto rotation cycle of the developing sleeve is effectively suppressed toprovide higher quality images.

Incidentally, the developing sleeve is supported by a developingapparatus unit by the medium of the flanges fastened to its ends and isrotated about the central axes of the flanges. At this time, if thecentral axes of the flanges and the central axis of the cylindersubstrate are deviated, the developing sleeve is rotated in an unstablemanner to cause pitch irregularity leading to inferior image qualities.According to the above embodiment, however, the flanges can be fastenedat a further improved accuracy, so that the occurrence of the pitchirregularity is effectively alleviated to provide high quality images.

Incidentally, this embodiment of inner surface-processing of a cylindercan also be applied to photosensitive drums, etc., as explained withreference to FIGS. 1-6.

Now, an embodiment of a process cartridge which the above embodimentscan be applied will be described with reference to FIG. 14.

Referring to FIG. 14, a process cartridge 50 according to thisembodiment comprises an electrophotographic photosensitive drum 3 as animage bearing member, and charging means 102, developing means 104containing a toner (developer) and cleaning means 106 disposed aroundthe photosensitive drum 3. These members are integrally disposed withina housing 50a to form a cartridge, which is detachably mountable to themain assembly of an image forming apparatus.

The respective parts of the process cartridge will now be described.

The photosensitive drum 101 (3) comprises an aluminum cylinder 3a1coated with an organic photoconductive layer 3a2 on its outer peripheralsurface, and both ends of the drum axis 101a (3a) are rotatablysupported by the housing 50a. A driving force from a drive motor (notshown) is transmitted via a helical gear 6 (FIG. 1) to a helical gear 1connected to the photosensitive drum 101 (3) to rotate thephotosensitive drum in the direction of an arrow A according to an imageforming operation. The photosensitive drum 3 may be constituted byapplying the above embodiment described with reference to FIGS. 1-6or/and the embodiment described with reference to FIGS. 9-13.

The charging means 102 is of the so-called contact charging type andcomprises an electroconductive roller 102a, which is caused to contactthe photosensitive drum 3 and is supplied with a voltage to uniformlycharge the surface of the photosensitive drum 3. The roller 102a ispushed against the drum 3 by a spring 102b.

The process cartridge 50 is further provided with an exposure section50b where the photosensitive drum 3 charged by the above-mentionedcharging means 102 is exposed to image light issued from an apparatusmain assembly and entering through the exposure slit 50c.

The developing means 104 is disposed to visualize the electrostaticlatent image by development with a toner.

As shown in FIG. 14, the developing means 104 comprises a container 104afor storing the toner and a toner feeding mechanism 104b disposed withinthe container 104a and rotates to feed the toner to the forward sectionof the container 104a where a developing sleeve 30 and a blade 104c aredisposed.

In image formation, the developing means is driven to successively formvisual images with the toner on the photosensitive drum 3. Morespecifically, the toner within the container 104a is fed to the forwardsection thereof by the toner feeding mechanism 104b, and the toner isapplied in a thin charged layer on the circumference of the rotatingsleeve 30 by the blade 104c. A developing bias is applied between thesleeve 30 and the photosensitive drum 3 bearing a latent image, thelatent image is developed with the toner. The developing sleeve 30 isformed according to the embodiment described with reference to FIGS.9-13.

The position of the developing means is determined by aposition-determining mechanism (not shown) so as to confront thephotosensitive drum 3 with a minute clearance (on the order of 250 μm).The sleeve 30 is connected to a high-voltage source disposed within theapparatus main assembly and is supplied with a voltage for development.Inside the sleeve 30, a magnet 30a is formed to assist the formation andcharging of the thin toner layer.

The toner image formed on the photosensitive drum 3 by the developingmeans 104 position-determined with respect to the photosensitive drum 3is transferred to a recording medium such as paper (not shown) which ismoved below the photosensitive drum 3. Before the use of the processcartridge which is mounted to the apparatus main assembly in use,however, the photosensitive drum 3 is covered with a protective cover 50attached to the housing 50 so as to allow opening and closing thereoffor the purpose of preventing attachment of dirt, etc., anddeterioration by exposure to external light of the photosensitive drumcaused when the photosensitive drum 3 is exposed to the atmosphere.

The protective cover 50d is attached so as to be openable in thedirection of an arrow B in FIG. 14 and is urged to be closed by aspring, etc. (not shown). When the process cartridge 50 is taken out ofthe apparatus main assembly, the protective cover 50d is in the closedstate as shown in FIG. 14. When the process cartridge 50 is mounted tothe apparatus main assembly, the protective cover 50 is moved in thearrow B direction to be opened by a mechanism (not shown), so that thephotosensitive drum 3 confronts a transfer roller (not shown) on whichpaper is moved in image formation.

The exposure section 50b is also equipped with a protective cover (notshown) which is opened when the cartridge is mounted to the apparatusmain assembly.

The cleaning means 106 is disposed to remove residual toner on thephotosensitive drum 3 remaining after transfer of the toner image to therecording medium (paper). The cleaning means 106 includes a toner vessel106a for receiving the residual toner, an elastic blade 106b and ascooping sheet 106c. Upon rotation of the photosensitive drum 3, theresidual toner remaining on the photosensitive drum 3 is scraped by theblade 106b and guided by the scooping sheet 106c into the waste tonervessel 106a.

The process cartridge integrally includes a charging means, a developingmeans and/or a cleaning means together with an electrophotographicphotosensitive member and is detachably mountable to an apparatus mainassembly. It is preferred that at last the developing means and theelectrophotographic photosensitive member are integrated to provide acartridge.

In the above-described embodiments, the image-bearing member may have animage-bearing layer which may comprise an electrophotographicphotosensitive material such as an organic photoconductor or amorphoussilicon photoconductor, or may simply be an insulating layer. Such animage-bearing layer may preferably be formed on a cylinder except for aportion thereof bent and cut for fastening.

The above-described embodiments can be applied separately or incombination. The resultant cylindrical structure may for example be aphotosensitive drum, a conveying roller, a fixing roller or a developingsleeve. These cylindrical structures may be directly assembled to forman image forming apparatus, or some of them may be integrated to form acartridge which is detachably mountable to an apparatus main assembly.

As described hereinabove, according to the present invention, there areprovided a method of fastening an engaging member to an end of acylinder to provide a sufficient engaging force, a cylindrical structurethus obtained, a process cartridge and an image forming apparatusincluding such a cylindrical structure. further, by combining the innersurface-processing for socket joint, a further accurate engagement isensured.

What is claimed:
 1. A method of fastening an engaging member to an openend of a cylinder, said method comprising the steps of:processing aninner surface of the open end of the cylinder to provide the cylinderwith a reduced thickness; providing an engaging member having aplurality of discrete recesses formed circumferentially around aperiphery of the engaging member; fitting the engaging member into theprocessed open end of the cylinder; and bending and cutting theprocessed open end of the cylinder, at positions spacedcircumferentially around the open end of the cylinder, such that aplurality of parts projects into the plurality of discrete recesses ofthe engaging member, thereby restricting relative movement between thecylinder and the engaging member in longitudinal and rotationaldirections, wherein the engaging member is press-fit into the cylinder.2. A method according to claim 1, wherein the inner surface of thecylinder is processed by at least one of cutting, abrading and grindingso as to provide an improved engagement accuracy between the cylinderand the engaging member.
 3. A method according to claim 1, wherein thecylinder is bent and cut at circumferentially mutually opposite portionsof an end brim of the cylinder.
 4. A method according to claim 1,wherein the cylinder is bent and cut substantially simultaneously.
 5. Amethod according to claim 1, wherein the cylinder is first bent and thencut on further bending.
 6. A method according to claim 1, wherein theengaging member is a plastic flange, the plastic flange being fastenedto the cylinder, the cylinder containing a magnet therein to provide adeveloping sleeve.
 7. A method according to claim 1, wherein thecylinder has a thickness in the range of 0.3-1.5 mm in the vicinity ofthe plurality of parts.
 8. A method according to claim 1, wherein thecylinder is cut in a length of at least 0.2 mm.
 9. A method of fasteningan engaging member to an open end of a cylinder, said method comprisingthe steps of:processing an inner surface of the open end of the cylinderto provide the cylinder with a reduced thickness; providing an engagingmember having a plurality of discrete recesses formed circumferentiallyaround a periphery of the engaging member; fitting the engaging memberinto the processed open end of the cylinder; and bending and cutting theprocessed open end of the cylinder, at positions spacedcircumferentially around the open end of the cylinder, such that aplurality of parts projects into the plurality of discrete recesses ofthe engaging member, thereby restricting relative movement between thecylinder and the engaging member in longitudinal and rotationaldirections, wherein the engaging member is press-fit into the cylinderwith a press fit margin of 5-180 μm.
 10. A method according to claim 1,wherein the cylinder comprises aluminum.
 11. A method according to claim1, wherein the engaging member comprises an insulating flange.
 12. Amethod according to claim 1, wherein the engaging member comprises agear.
 13. A method according to claim 1, wherein the cylinder has asurface comprising a photosensitive material, and wherein the engagingmember is a gear, the gear being fastened to an end of the cylinder toprovide a photosensitive drum.
 14. A method according to claim 13,wherein the gear is a helical gear.
 15. A method according to claim 1,wherein the engaging member is a plastic flange, the plastic flangebeing fastened to the cylinder to provide a developing sleeve.
 16. Amethod according to claim 9, wherein the engaging member is a plasticflange, the plastic flange being fastened to the cylinder, the cylindercontaining a magnet therein to provide a developing sleeve.
 17. A methodaccording to claim 9, wherein the inner surface of the cylinder isprocessed by at least one of cutting, abrading and grinding so as toprovide an improved engagement accuracy between the cylinder and theengaging member.
 18. A method according to claim 9, wherein the cylinderis bent and cut at circumferentially mutually opposite portions of anend brim of the cylinder.
 19. A method according to claim 9, wherein thecylinder is bent and cut substantially simultaneously.
 20. A methodaccording to claim 9, wherein the cylinder is first bent and then cut onfurther bending.
 21. A method according to claim 9, wherein the cylinderhas a thickness in the range of 0.3-1.5 mm in the vicinity of theplurality of parts.
 22. A method according to claim 9, wherein thecylinder is cut in a length of at least 0.2 mm.
 23. A method accordingto claim 9, wherein the cylinder comprises aluminum.
 24. A methodaccording to claim 9, wherein the engaging member comprises aninsulating flange.
 25. A method according to claim 9, wherein theengaging member comprises a gear.
 26. A method according to claim 9,wherein the cylinder has a surface comprising a photosensitive material,and wherein the engaging member is a gear, the gear being fastened to anend of the cylinder to provide a photosensitive drum.
 27. A methodaccording to claim 26, wherein the gear is a helical gear.
 28. A methodaccording to claim 9, wherein the engaging member is a plastic flange,the plastic flange being fastened to the cylinder to provide adeveloping sleeve.
 29. A method of assembling a developing sleeve foruse in an electrophotographic image forming apparatus, said methodcomprising the steps of:providing a cylinder having a developer-carryingouter surface and an open end having an inner surface; processing theinner surface of the cylinder to provide the cylinder with a reducedthickness; providing a terminal engaging member including a head whichhas a plurality of discrete recesses formed circumferentially around aperiphery of the head; press-fitting the head of the terminal engagingmember into the processed open end of the cylinder; and bending andcutting the processed open end of the cylinder such that a plurality ofparts projects into the plurality of discrete recesses of the head,thereby restricting relative movement between the cylinder and theterminal engaging member in longitudinal and rotational directions. 30.A method according to claim 29, wherein the inner surface of thecylinder is processed by at least one of cutting, abrading and grindingso as to provide an improved engagement accuracy between the cylinderand the engaging member.
 31. A method of assembling anelectrophotographic photosensitive drum for use in anelectrophotographic image forming apparatus, said method comprising thesteps of:providing a cylinder having an image-bearing outer surface andan open end having an inner surface; processing the inner surface of thecylinder to provide the cylinder with a reduced thickness; providing aterminal engaging member including a head which has a plurality ofdiscrete recesses formed circumferentially around a periphery of thehead; press-fitting the head of the terminal engaging member into theprocessed open end of the cylinder; and bending and cutting theprocessed open end of the cylinder such that a plurality of partsprojects into the plurality of discrete recesses of the head, therebyrestricting relative movement between the cylinder and the terminalengaging member in longitudinal and rotational directions.
 32. A methodaccording to claim 29, wherein the cylinder is bent and cut atcircumferentially mutually opposite portions of an end brim of thecylinder.
 33. A method according to claim 29, wherein the cylinder isbent and cut substantially simultaneously.
 34. A method according toclaim 29, wherein the cylinder is first bent and then cut on furtherbending.
 35. A method according to claim 29, wherein the cylinder has athickness in the range of 0.3-1.5 mm in the vicinity of the plurality ofparts.
 36. A method according to claim 29, wherein the cylinder is cutin a length of at least 0.2 mm.
 37. A method according to claim 29,wherein the engaging member is press-fit into the cylinder with apress-fit margin of 5-180 μm.
 38. A method according to claim 29,wherein the cylinder comprises aluminum.
 39. A method according to claim29, wherein the engaging member comprises an insulating flange.
 40. Amethod according to claim 29, wherein the engaging member is a plasticflange, the plastic flange being fastened to the cylinder to provide adeveloping sleeve.
 41. A method according to claim 29, wherein theengaging member is a plastic flange, the plastic flange being fastenedto the cylinder, the cylinder containing a magnet therein to provide adeveloping sleeve.
 42. A method according to claim 31, wherein theengaging member comprises a gear.
 43. A method according to claim 31,wherein the inner surface of the cylinder is processed by at least oneof cutting, abrading and grinding so as to provide an improvedengagement accuracy between the cylinder and the engaging member.
 44. Amethod according to claim 31, wherein the cylinder is bent and cut atcircumferentially mutually opposite portions of an end brim of thecylinder.
 45. A method according to claim 31, wherein the cylinder isbent and cut substantially simultaneously.
 46. A method according toclaim 31, wherein the cylinder is first bent and then cut on furtherbending.
 47. A method according to claim 31, wherein the cylinder has athickness in the range of 0.3-1.5 mm in the vicinity of the plurality ofparts.
 48. A method according to claim 31, wherein the cylinder is cutin a length of at least 0.2 mm.
 49. A method according to claim 31,wherein the engaging member is press-fit into the cylinder with apress-fit margin of 5-180 μm.
 50. A method according to claim 31,wherein the cylinder comprises aluminum.
 51. A method according to claim31, wherein the cylinder has a surface comprising a photosensitivematerial, and wherein the engaging member is a gear, the gear beingfastened to an end of the cylinder to provide a photosensitive drum. 52.A method according to claim 31, wherein the gear is a helical gear.